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Diffstat (limited to 'src/fortran/lapack/dlanhs.f')
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diff --git a/src/fortran/lapack/dlanhs.f b/src/fortran/lapack/dlanhs.f new file mode 100644 index 0000000..76b87ee --- /dev/null +++ b/src/fortran/lapack/dlanhs.f @@ -0,0 +1,141 @@ + DOUBLE PRECISION FUNCTION DLANHS( NORM, N, A, LDA, WORK ) +* +* -- LAPACK auxiliary routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER NORM + INTEGER LDA, N +* .. +* .. Array Arguments .. + DOUBLE PRECISION A( LDA, * ), WORK( * ) +* .. +* +* Purpose +* ======= +* +* DLANHS returns the value of the one norm, or the Frobenius norm, or +* the infinity norm, or the element of largest absolute value of a +* Hessenberg matrix A. +* +* Description +* =========== +* +* DLANHS returns the value +* +* DLANHS = ( max(abs(A(i,j))), NORM = 'M' or 'm' +* ( +* ( norm1(A), NORM = '1', 'O' or 'o' +* ( +* ( normI(A), NORM = 'I' or 'i' +* ( +* ( normF(A), NORM = 'F', 'f', 'E' or 'e' +* +* where norm1 denotes the one norm of a matrix (maximum column sum), +* normI denotes the infinity norm of a matrix (maximum row sum) and +* normF denotes the Frobenius norm of a matrix (square root of sum of +* squares). Note that max(abs(A(i,j))) is not a consistent matrix norm. +* +* Arguments +* ========= +* +* NORM (input) CHARACTER*1 +* Specifies the value to be returned in DLANHS as described +* above. +* +* N (input) INTEGER +* The order of the matrix A. N >= 0. When N = 0, DLANHS is +* set to zero. +* +* A (input) DOUBLE PRECISION array, dimension (LDA,N) +* The n by n upper Hessenberg matrix A; the part of A below the +* first sub-diagonal is not referenced. +* +* LDA (input) INTEGER +* The leading dimension of the array A. LDA >= max(N,1). +* +* WORK (workspace) DOUBLE PRECISION array, dimension (MAX(1,LWORK)), +* where LWORK >= N when NORM = 'I'; otherwise, WORK is not +* referenced. +* +* ===================================================================== +* +* .. Parameters .. + DOUBLE PRECISION ONE, ZERO + PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 ) +* .. +* .. Local Scalars .. + INTEGER I, J + DOUBLE PRECISION SCALE, SUM, VALUE +* .. +* .. External Subroutines .. + EXTERNAL DLASSQ +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. Intrinsic Functions .. + INTRINSIC ABS, MAX, MIN, SQRT +* .. +* .. Executable Statements .. +* + IF( N.EQ.0 ) THEN + VALUE = ZERO + ELSE IF( LSAME( NORM, 'M' ) ) THEN +* +* Find max(abs(A(i,j))). +* + VALUE = ZERO + DO 20 J = 1, N + DO 10 I = 1, MIN( N, J+1 ) + VALUE = MAX( VALUE, ABS( A( I, J ) ) ) + 10 CONTINUE + 20 CONTINUE + ELSE IF( ( LSAME( NORM, 'O' ) ) .OR. ( NORM.EQ.'1' ) ) THEN +* +* Find norm1(A). +* + VALUE = ZERO + DO 40 J = 1, N + SUM = ZERO + DO 30 I = 1, MIN( N, J+1 ) + SUM = SUM + ABS( A( I, J ) ) + 30 CONTINUE + VALUE = MAX( VALUE, SUM ) + 40 CONTINUE + ELSE IF( LSAME( NORM, 'I' ) ) THEN +* +* Find normI(A). +* + DO 50 I = 1, N + WORK( I ) = ZERO + 50 CONTINUE + DO 70 J = 1, N + DO 60 I = 1, MIN( N, J+1 ) + WORK( I ) = WORK( I ) + ABS( A( I, J ) ) + 60 CONTINUE + 70 CONTINUE + VALUE = ZERO + DO 80 I = 1, N + VALUE = MAX( VALUE, WORK( I ) ) + 80 CONTINUE + ELSE IF( ( LSAME( NORM, 'F' ) ) .OR. ( LSAME( NORM, 'E' ) ) ) THEN +* +* Find normF(A). +* + SCALE = ZERO + SUM = ONE + DO 90 J = 1, N + CALL DLASSQ( MIN( N, J+1 ), A( 1, J ), 1, SCALE, SUM ) + 90 CONTINUE + VALUE = SCALE*SQRT( SUM ) + END IF +* + DLANHS = VALUE + RETURN +* +* End of DLANHS +* + END |